1. Field of the Invention
This invention relates to a toner for electrophotographic process. More particularly, it relates to toners for electrophotographic process which comprise a specific phenolic compound.
2. Description of the Prior Art
Electrophotographic (imaging) process referred to as xerographic imaging process or xerography are well known (U.S. Pat. No. 4066563, etc.)
General methods for image formation utilizing static electricity comprise charging toners by contact friction with carriers such as glass beads, iron powders, etc., allowing to develop an electrostatic latent image formed on a photoreceptor made of a photoconductive material (selenium, zinc oxide, cadmium sulfide, etc.) and further fixing the developed image by heat, pressure, etc.
In general, colored fine particles called toners comprise a binder as a principal component, a colorant and a charge control agent as essential components and furthermore a fluidizing agent, an antifoggant, etc., among which a charge control agent which has functions of preservation of charge produced by friction with carriers and regulation of charge characteristics of toners is an especially important component in the toner components.
Quality characteristics required for toners are chargeability and charge durability (an ability to maintain a charge for a long time), fluidity, etc. and these are all greatly influenced by a charge control agent used.
Hitherto, as charge control agents for toners, there have been known 2:1 type metal complex dyes [Japanese Patent Publication (Kokoku) Nos. 26478/70 and 201531/66], phthalocyanine pigment [Japanese Patent Application Kokai (Laid-open) No. 45931/77], metallic complexes of salicylic acid Japanese Patent Application Kokai (Laid-open) No. 122726/78), metallic complexes of aromatic dicarboxylic acids [Japanese Patent Publication (Kokoku) No. 7384/84], nigrosine dyes, various quaternary amines (The Journal of Electrostatic Society, 1980, Vol. 4, No. 3, Page 144). However, toners having such charge control agents do not satisfy the quality characteristics required for toners such as chargeability, durability of charge etc.
For example, toners containing 2:1 metal complex dyes known as negative charge control agents show a moderate level in chargeability, but are poor in adhesion property to bases such as paper and are not satisfactory in moisture resistance and so are low in durability of charge. Thus, they are inferior in repetition property in image formation (copy).
Furthermore, 2:1 metal complex dyes have the that they can be used only for black toners or toners having hues near to black because they have black hue or hues near to black. As a nearly colorless negative charge control agent, there are metal complexes of aromatic dicarboxylic acid [Japanese Patent Publication (Kokoku) No. 7384/84], but they also have defects that they cannot become completely colorless and are inferior to 2:1 metal complex dyes in chargeability. As colorless negative charge control agents which are similar to 2:1 metal complex dyes in chargeability, there are compounds reported in Japanese Patent Application Kokai (Laid-open) No. 3149/86, but since melting points of such compounds are lower than a processing temperature (180.degree.-260.degree. C.) in preparing toners various troubles occur and preparation of stable toners is difficult.
Development of toners has been demanded which are superior in chargeability and charge durability and show stable processability at preparation thereof with use of charge control agents which are colorless and have a wide variety of applications. Furthermore, use of charge control agents free from heavy metals is preferred for prevention of environmental pollution.